Bipolar surface element

Abstract

A bipolar flat element comprising a coating that contains expanded graphite and a binder, the coating being applied to at least one of the two primary surfaces of a flat, electrically conductive element.

1 - 15 . (canceled) 
     
     
         16 . A bipolar flat element comprising a coating that comprises expanded graphite and a binder, wherein the coating is applied to at least one of two primary surfaces of a flat, electrically conductive element. 
     
     
         17 . The bipolar flat element according to  claim 16 , wherein the flat, electrically conductive element is a metallic flat element. 
     
     
         18 . The bipolar flat element according to  claim 16 , wherein the flat, electrically conductive element is a graphite-comprising flat element. 
     
     
         19 . The bipolar flat element according to  claim 18 , wherein the flat element comprises expanded graphite. 
     
     
         20 . The bipolar flat element according to  claim 18 , wherein a mass fraction of binder comprised in the coating is higher than a mass fraction of binder of the flat element. 
     
     
         21 . The bipolar flat element according to  claim 16 , wherein an area-specific volume resistivity of the bipolar flat element is at most 20 mΩ•cm 2 . 
     
     
         22 . The bipolar flat element according to  claim 16 , wherein the binder comprises thermoplastics and/or thermosets. 
     
     
         23 . The bipolar flat element according to  claim 16 , wherein the binder comprises a silicon compound comprising a moiety R, wherein
 R stands for —Si(OR 1 )(OR 2 )(OR 3 ), —O—Si(OR 1 )(OR 2 )(R 3 ), or —O—Si(OR 1 )(OR 2 )(OR 3 ), wherein   R 1 , R 2  and R 3  are moieties each bonded via a carbon atom.   
     
     
         24 . The bipolar flat element according to  claim 16 , wherein the coating comprises a dispersing agent. 
     
     
         25 . The bipolar flat element according to  claim 16 , wherein the thickness of the coating is in the range of from 5 to 500 µm. 
     
     
         26 . The bipolar flat element according to  claim 16 , wherein regions in the coating comprising the expanded graphite have an average length parallel to the surfaces of the coating that is at least twice as large as their average thickness. 
     
     
         27 . The bipolar flat element according to  claim 16 , wherein, in the coating, the ratio Qs, which is calculated according to the following equation: 
       
         
           
             
               
                 Q 
                 S 
               
                 
               = 
                 
               
                 
                   
                     m 
                     
                       SG 
                     
                   
                 
                 
                   
                     m 
                     
                       SR 
                     
                   
                 
               
             
           
         
       
        wherein
 m SG  stands for the mass of the graphite comprised in the coating, and 
 m SR  stands for the mass of the non-volatile coating components comprised in the coating, 
 is at least 0.25. 
 
     
     
         28 . The bipolar flat element according to  claim 16 , obtainable by applying a coating agent to a flat, electrically conductive element,
 wherein the coating agent comprises expanded graphite and a binder.   
     
     
         29 . A fuel cell or redox flow battery, having a bipolar flat element according to  claim 16 . 
     
     
         30 . A method for producing a bipolar flat element, wherein a coating agent comprising expanded graphite and a binder is applied to a flat, electrically conductive element. 
     
     
         31 . The bipolar flat element according to  claim 19 , wherein a mass fraction of binder comprised in the coating is higher than a mass fraction of binder of the flat element.